Photographic plate development system

ABSTRACT

A photographic plate development system for batch processing of photographic plates to provide consistent and high quality plates. The system is comprised of a processor tank having a removable plate supporting rack for supporting the plates in parallel, vertical planes. The processor tank has electrodes at the bottom thereof under the normal position of the plates, and vertical electrodes disposed in the tank adjacent the emulsion side of the plate. The bottom electrodes are provided with a negative polarity with respect to the vertical electrodes when the processor tank is filled with an appropriate developing solution. The resulting electrolysis causes hydrogen bubbles to be produced at the bottom electrodes and rise through the developer along the emulsion surface to provide a gentle turbidity over the entire emulsion surface. The negatively charged particular by-products of the development are encouraged to break away from the emulsion surface by the turbidity and are attracted to the vertical electrode by electrophoretic attraction. The developer and fixer are delivered to the processor tank under pressure, and a drain pump is provided to allow the rapid draining of the processor tank. An outer tank is provided around the processor tank for containing and rinsing away any slop-over from the processor tank.

i United States Patent 1 [111 3,739,705 June 19, 1973 Lasky PHOTOGRAPHIC PLATE DEVELOPMENT SYSTEM [75} Inventor: Daniel J. Lasky, San Jose, Calif. [73] Assignee: U.S. Electra-Optical Incorporated,

' Santa Ana, Calif. 22 Filed: Nov. 1, 1971 [21] Appl. No.: 194,727

[52] U.S. Cl. 95/89 R, 204/299 R [51] Int. Cl. 603d 3/10 [58] Field of Search 95/89 R, 94 R, 96,

[56'] References Cited 1 UNITED STATES PATENTS 3,615,515 10/1971 Lasky..... 95/89 RX 3,000,288 9/1961 Winnek... 95/96 X 1,802,192 4/1931 Caps 95/97 2,356,536 8/1944 Rzymkowski 95/89 R UX 3,440,160 4/1969 Matkovich 204/299 R X 3,508,483 4/1970 Weider et a1. 95/96 Primary Examiner-Samuel S. Matthews Assistant Examiner-Fred L. Braun Attorneyi-Spensley, Horn and Lubitz [5 7 ABSTRACT A photographic plate development system for batch processing of photographic plates to provide consistent and high quality plates. The system is comprised of a processor tank having a removable plate supporting rack for supporting the plates in parallel, vertical planes. The processor tank has electrodes at the bottom thereof under the normal position of the plates, and vertical electrodes disposed in the tank adjacent the emulsion side of the plate. The-bottom electrodes are provided with a negative polarity with respect to the vertical electrodes when the processor tank is filled with an appropriate developing solution. The resulting electrolysis causes hydrogen bubbles to be produced at the bottom electrodes and rise through the developer along the emulsion surface to provide a gentle turbidity over the entire emulsion surface. The negatively charged particular by-products of the development are encouraged to break away from the emulsion surface by the turbidity and are attracted to the vertical electrode by electrophoretic attraction. The developer and fixer are delivered to the processor tank under pressure, and a drain pump is provided to allow the rapid draining of the processor tank. An outer tank is provided around the processor tank for containing and rinsing away any s1op-over from the processor tank.

14 Claims, 10 Drawing Figures Patented June 19, 1973 3 Sheets-Sheet 1 MHAHI A/meoazw a? I Patented June 19, 1973 3 Sheets-Sheet 2 PHOTOGRAPHIC PLATE DEVELOPMENT SYSTEM This invention relates to the field of photographic plate processing systems of the batch processing type.

2. Prior Art Various systems are well-known in the prior art for the automatic development of film, such as movie film, X-ray film and the like. However, automatic processing systems for batch processing of photographic plates wherein a photosensitive emulsion is disposed on one surface of a solid and inflexible plate, rather than the typical cellulose acetate or cellulose nitrate backing as used in movie film, are not known in the prior art, either for a continuous flow process or for automatic batch processing. Instead, individual plates or batches of plates are processed manually through the usual developers, fixers, and washers to achieve the desired result. (One system is known in the prior art for automatic processing of plates, comprising a conveyor system for transporting plates past a plurality of appropriate sprays. This system is more convenient than manual processing for large numbers of plates, but does not yield a substantially improved uniformity in development.)

The manual handling and/or spray processing of plates through a conventional developing process provides satisfactory results for most applications. However, in certain applications, such as in the production of photomasks to be used in integrated circuit device fabrication, the photomask must be of the best quality possible, with the best edge definition or image sharpness possible, and without any flaws in the pattern or edge definition which would cause failure of the resulting integrated circuit device. Consequently, uniformity of development over the entire plate area, from plate to plate, and uniformity of results from batch to batch, and the absence of contamination are exceptionally important objects of any system for developing photographic plates to be used as such photomasks. To emphasize the above objects, it is to be noted that circuit elements of only a fraction of a thousandth of an inch in width are now being produced, such elements being defined by the masks during the processing period. Further, even smaller elements are desirable since smaller elements allow the placement of more elements on a given semiconductor chip, allowing the placement of more circuitry on one chip and the resulting reduction in the number of external connections which must be made, all without significantly increasing the. production costs of the item since the processing remains the same. Further, smaller elements result in lower signal propagation times, both because of the resulting shorter conduction paths and in the reduction of capacitive coupling.

It should be noted that photomasks for semiconduc- 'tor device fabrication, unlike movie film, X-ray film and the like, are comprised of patterns of transparent and opaque areas with a required very sharp line of demarkation therebetween (e.g., edgedefinition), and gradations of opaqueness are neither desired nor tolerable. Therefore, it may be seen that a simple system is required for the automatic development of photographic plates which will yield photomasks of the highest quality with a minimum opportunity for operator error and contamination.

BRIEF SUMMARY OF THE INVENTION A photographic plate development system for batch processing of photographic plates to provide consistent and high quality plates. The system is comprised of a processor tank having a removable plate supporting rack for supporting the plates in parallel vertical planes and is located within a laminar flow hood to prevent airborne contamination from entering the tank. The processor tank has electrodes at the bottom thereof under the normal position of the plates, with an edge of such electrodes vertically aligned with the sensitized surface of the plates, and further, has vertical electrodes disposed in the tank adjacent the sensitized side of the plates. The bottom electrodes, in the preferred embodiment, are stainless steel, and the side electrodes are platinum plated titanium electrodes, generally of open construction so as to define an electrostatic plane, but not interfere with the flow of solutions therethrough. The bottom electrodes are provided with a negative polarity with respect to the vertical electrodes when the processor tank is filled with an appropriate developing solution. This causes electrolysis of the solution, creating hydrogen bubbles at the bottom electrodes which are released at the edge of the electrodes and rise through the developer along the sensitized surface to provide a gentle turbidity over the entire emulsion surface. The negatively charged particular byproducts of the development are encouraged to break away from the emulsion surface by the turbidity and are attracted to'the vertical electrode by electrophoretic attraction.

The developer and fixer are delivered to the processor tank under pressure, and a drain pump is provided to allow the rapid draining of the processor tank. An outer tank is provided around the processor tank ito provide a means for containing and rinsing away ajny spillage from the processor tank. A timing meansi is provided for timing and automatically sequencing the various electrical devices controlling the system, specifically, the wash water, rinse water, the drain pump, and the fixer solenoid valves, and the development voltage applied to the electrodes. 1

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the apparatus of the present invention.

FIG. 2 is a block diagram illustrating the major functional components of the apparatus of FIG. 1.

FIG. 3 is a cross-section of the tank 30, showing the normal disposition of the process tank, rack, plate holders and electrodes. 1

FIG. 3a is a cross-section of the tank 30 taken on a plane perpendicular to the longitudinal axis of the tank,

further illustrating thenormal disposition of the tank, rack, plate holders and electrodes FIG. 4 is a side view of a portion of the rack and of a plate holder of FIG. 3, shown on an expanded scale.

FIG. 5 is a cross-section of the plate holder of FIG. 4 taken along lines 5--5 of that figure.

FIG. 6 is an illustration of the manner in which hydrogen bubbles are emitted by the stainless steel electrodes to flow along the sensitized surface of a plate and the electrophoretic attraction of the particular byv products to the vertical electrodes.

FIGS. 7a-7c are illustrations of the timing apparatus and sequence for the various control devices in the apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION First referring to FIG. 1, a perspective view of one embodiment of the present invention may be seen. In this embodiment, the processor comprises a cabinet, generally indicated by the numeral 20, with a lower portion 22 housing the processor tanks, pumps and the like and, in the area generally indicated by the numeral 24, a pair of processing solution tanks, and in the upper section 26, filters, fans and the like for drawing in air from above, filtering the air and delivering it in a nonturbulent manner to the opening 28 above the main processor tank. Thus, filtered air is delivered behind the processor area, generally indicated by the numeral 29, creating a gentle but definite forward movement of filtered air over the processor tanks and outward through the front of the processing system. Consequently, any contamination in the air in the room in which the processor is being used may not settle into the processor tank since the flow of air across the top of the processor tank prevents the dust from entering under the top portion 26 of the cabinet. Such air flow systems are commonly referred to as laminar flow systems and have heretofore been used in covered assembly benches for precision instruments and the like.

Located just forward of the processor area 29 is a dryer section 31. The dryer section is adapted to receive and support a rack full of plates, (specifically, rack 68 subsequently described), and to provide a flow of heated and filtered air around the plates to dry the plates. Details of the structure of the dryer section are not disclosed herein as air blowers, heaters and filters are well-known, and any reasonable disposition of these well-known components will serve the purpose. Of course, excessively violent air flow or excessive temperatures are to be avoided as mechanical damage or distortion of the film may result therefrom. The disposal of the dryer section under the laminar flow hood allows the movement of developed plates into the dryer section without exposing them to possible contamination.

Now referring to FIG. 2, a schematic diagram of the processor tank and associated apparatus of the processing system of FIG. 1 may be seen. An inner-processor tank 30 provides a support for a rack 32, which in turn may support a plurality of plate holders 34, each of which may support in parallel spaced apart relationship a pair of plates. Directed into the tank 30 is a first conduit 36 for connection to a source of wash water, through a solenoid valve 58, a second conduit 38 connected to a tank 40 through solenoid valve 52, and a third conduit 42 connected to a tank 44 through solenoid valve 56. An outlet line 46 connected to a drain through a pump 48 provides a means of emptying the inner tank. A line 50 connects tank 40 to a source of high pressure air ,or nitrogen, and similarly, tank 44 is connected by line 54 to the same source of nitrogen or air. In operation, as shall be subsequently described in greater detail, tank 40 may be filled with developer and tank 44 may be filled with a fixer or hypo, and by operation of the solenoid valves, tank 30 may be quickly filled with developer or hypo as desired as a result of the high pressure gas forcing the solutions out of tanks 40 and 44 into tank 30 as desired. Similarly, tank 30 may be rapidly emptied of developer, fixer or wash water at the end of the various cycles by means of pump 48, and tank 30 may be rapidly filled with wash water under pressure through line 36 through wash water solenoid vale 58.

An outer tank is disposed adjacent to tank 30 so as to retain and direct through drain 62 any overflow from tank 30. A water manifold system 64 is disposed around tank 30 within tank 60 and may be supplied with rinse water through solenoid valve 66 so as to direct a spray to cleanse the outer wall of tank 30. The purpose of this is to wash off any excess developer spillover which may have occurred during plate loading and is necessary because of subsequent chemical usage where incompatibility produces irritating fumes when mixing even small quantities of such chemicals is allowed.

Now referred to FIG. 3, additional details of the inner-tank and associated structure may be seen. A rack 68 may be inserted into tank 30 so as to be supported by the top edges thereof. The rack 68 provides a means for supporting a plurality of plate holders 70 in parallel equally spaced apart relationship below the normal level of the various solutions in the tank. Generally located under the position normally occupied by each plate holder is an electrode 72, with the plurality of electrodes 72 connected in series through line 74 to the negative terminal of a power source 76. A plurality of electrodes 78 are disposed in a vertical relation parallel to and spaced slightly away from each side of the plate holder with all of the electrodes 78 connected in series through line 80 and through a switch 82 to the positive terminal of the DC power supply 76.

Now referring to FIGS. 4 and 5, further details of the plate rack and plate holders may be seen. FIG. 4 is a side view of one of the plate holders 34 in the rack 68. The rack 68 is comprised of a pair of parallel side members 82 spaced apart so as to accept the plate holders 34 therebetween, with a plurality of depressions 84 therein to locate and support the plate holders 34 by means of pins 86 in the late holder. The plate holder has a pair of lower pins 88 through the base thereof to intercept the lower edge of the plates 90 and provide vertical support therefor. FIG. 5, which is a crosssection of a plate holder taken along line 5-5 of FIG. 4, shows the manner in which the plates are supported. The plates 90 are inserted into grooves 92 at each side of the plate holder with the emulsion surface 94 on the plate facing outward. The plate is engaged and supported only at its edges, with the center structure 96 of the plate holder being relieved behind the plate so as to define passages 98 therebehind.

Now referring to FIG. 6, a schematic representation illustrating the operation of the system may be seen. In this figure, one of the electrodes 78 and a portion of one of the electrodes 72 is shown, along with a plate 90 having its emulsion coated surface 94 facing the electrode. It is to be noted that the emulsion coated surface is disposed in a vertical plane substantially aligned with comer 100 of the electrode 72. When a voltage is applied between electrode 78 and electrode 72, with electrode 72 being a negative electrode, electrolysis of the solution occurs, with hydrogen ions (positive ions) being attracted to the electrode 72. The ions are electrically neutralized at the electrode, forming bubbles of hydrogen which are released from the sharp edges of the electrode and, in particular, the corner 100 of the electrode. These bubbles are normally minute, being approximately three to four thousandths of an inch in diameter, and since the electrode is positioned below, parallel to, and in close proximity to the emulsion surface of the photographic plate, their passage to the surface of the developer solution is evidenced by gentle turbidity over the whole emulsion surface. Also, since the emulsion has image areas corresponding to the circuit pattern on its surface, negatively charged particular by-products are formed in these areas. The turbidity generated by the rising hydrogen bubbles helps break these particles away from the emulsion surface. As soon as they are released, they are attracted to and held by the electrode 78 as a result of the electrophoretic attraction. The movement of these particular byproducts away from the emulsion surface helps cause fresh, unoxidized developer solution to occupy the former sight of the particle. Since more by-products are generated in large image areas, more turbidity is present than in the smaller image areas. Thus, image controlled agitation is achieved, that is, the agitation is controlled by the patterns of the image itself.

In the preferred embodiment, electrodes 72 are stainless steel electrodes and electrodes 78 are platinum plated titanium electrodes. In general, electrodes 78 are of a perforated or open structure so as to create an electrostatic surface without substantially interfering with the flow of the various solutions, etc. therethrough. These electrode materials were selected because of their compatibility with the various solutions commonly used, their resistance to participate in the various electro-chemical processes occurring within the processor tanks (e.g. their compatibility with the electrolytic cell makeup), and their resistance to oxidation when the processor tank is not being used. In the preferred embodiment, electrodes 78 are comprised of a wire mesh or screen of platinum plated titanium wire. The use of the plating rather than a solid platinum or platinum rhodium wire results in grossly reduced cost for these electrodes without sacrifice of the chemical and eIectro-chemical characteristics of the resulting electrode. a a

Now referring to FIGS. Ya-7c, and with reference also to FIG. 2 the operating cycle of the system of the present invention may be described. Tank 40 is initially filled with the desired developer solution and tank 44 is filled with the fixer solution. (A developer solution comprising six parts water to one part Kodak I-IRP developer concentrate and a fixer solution comprising eight parts water to one part of Kodak Rapid Fixer have been found to provide highly satisfactory results.) These two tanks are then sealed so that they may be pressurized to force the solutions into the processor tank 30 when desired. After these tanks are filled, plates are placed in the plate holders 70 in the proper orientation and the plate holders are in turn placed in rack 68. Thereafter, by means of a pushbutton switch, solenoid valve 52 is opened so that developer in tank 40 is forced through line 38 into the processor tank, the filling of the tank being observed and terminated when then desired level is achieved. Thereafter, the loaded rack 68 is placed into the processor tank 30 and the system is started by means of a switch, generally located on the control panel 29 (FIG. 1). This initiates a timing system 104 (FIG. 7;) which, in the preferred embodiment, comprises a time clock driving a plurality of cams, each of which operates a switch to program the appropriate electrical device coupled to the switch. Such devices are well-known in the prior art and are commonly used for sequencing and timing of electromechanical devices, and are characterized as providing a pre-programmed timing sequence which is automatically terminated at the end thereof.

FIG. 7a indicates the timing of the various electrical devices in the preferred embodiment, with FIG. 7b providing an explanatory listing of the information presented in FIG. 7a. Curve A indicates the on-off operation of the development voltage power supply, indicating the voltage wave form applied between electrodes 78 and 72. When the loaded rack is inserted into the developer solution and the system turned on, the development voltage power supply 76 is turned on approximately three times per minute, with approximately a 50 percent duty cycle during the first three minutes of the operating cycle. Thereafter, as indicated in curve C, the drain pump 48 is turned on for a sufficient length of time to empty the processor tank 30 of developer, and when the drain pump is thereafter turned off, the fixer solenoid valve is turned on as indicated in curve D to fill tank 30 with fixer solution immediately thereafter in a rapid manner. After soaking in fixer solution for approximately another three minutes, the drain pump 48 is again turned on to empty the processor tank 30 of fixer and immediately thereafter, the wash water solenoid 58 is actuated as indicated in FIGURE E. As indicated in FIG. 7a, two complete wash cycles are used in the preferred embodiment and wash water is allowed to spill over the processor tank 30 into the outer tank 60 and through the drain therefor, with the wash water initially being directed into the processor tank 30 so as to maintain a gentle flow of wash water past the emulsion surface on the plate. When the wash water solenoid is turned off for the second time (curve E), and the processor tank is pumped out (curve C) a final cam actuated switch generates a system clock pulse (curve F) which resets the system on-off switch. Thereafter, the rack is removed from the processor tank and placed in a forced air dryer section which provides a flow of filtered warm air past the plates so as to dry the plates prior to their removal.

By using the developing system of the present invention, extremely high quality photomasks may be fabricated on a repeatable and reliable basis. Possible opportunity for contamination is minimized with the processing occurring in a specially maintained benigned environment. The processing cycle is automatically controlled so that batch to batch variations may not occur. Furthermore, the automatic cycle control eliminates the possibility of operator error. Photomasks processed with the present invention have been sampled to determine the sharpness and accuracy of the edge definition obtained thereby and it has been found that 87 percent of all samples measured were within five millionths of an inch of the nominal dimension, with the remaining 13 percent ranging between five and eight millionths of an inch of the nominal dimension. This is to be compared with the results obtained on prior art equipment wherein a majority of the samples are found to be over ten millionths of an inch from the nominal dimension.

Thus, there has been described an automatic batch processor for photographic plates capable of consistently producing uniform and high quality photomasks. As used herein, the words photographic plates or plates are used in the general sense to indicate any plate having a sensitized surface thereon, and is not to be limited only to plates sensitive to light, and particularly visible light. Of course, while the preferred embodiment has been described herein in detail, variations therein and other embodiments may be readily fabricated as desired. By way of example, other types of sequencing which may provide adjustable sequence cycles and other operating cycles as well as a different design and arrangement of the functional parts, may readily be selected depending upon the application.

The operating cycle and solution delivery to the processor tank may be altered or expanded to provide for the delivery of other solutions, such as wetting agents or an alcohol-water solution for final rinsing to facilitate the subsequent drying of the plates, or to provide for a water stop bath between the developer and the fixer baths. Similarly, while the embodiment disclosed herein uses two wash cycles of approximately 2 minutes duration, one wash cycle of 8 minutes duration provides substantially the same result. Thus, while the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in forms and details may be made therein without departing from the spirit and scope of the invention.

I claim:

1. A processing apparatus for processing plates having a sensitized film on one surface thereof comprising:

a tank;

a rack for supporting a plurality of said plates within said tank;

at least one first electrode disposed in said tank below said rack;

a plurality of second electrodes disposed in said tank so as to each be substantially parallel to and adjacent the sensitized film on plates in said rack;

means for delivering processing fluids to said tank;

means for draining said fluids from said tank; means for applying a voltage between said at least one first electrode and said second electrodes; and

a laminar flow hood and a dryer section, said laminar flow hood being adapted to provide a gentle flow of filtered air over said tank and said dryer section, said dryer section being adapted to receive said rack and to direct warm, filtered air over plates in said rack.

2. The apparatus of claim 1 wherein said rack for supporting said plates is a rack for supporting said plates in substantially vertical and parallel planes and said at least one first electrode is a plurality of electrodes, each of which is disposed in said tank vertically below the normal position of at least one plate in said rack.

3. The apparatus of claim 2 wherein said rack is comprised of a rack member and a plurality of removable plate holders, said rack having a means of locating said plate holders in relation thereto, said plate holders being adapted to support at least one plate adjacent its edges so as to allow processing fluids to freely wet both sides of said plate.

4. The apparatus of claim 3 wherein said plate holders are adapted to support two plates in spaced apart parallel relationship, and each of said plurality of first electrodes is disposed below the normal position of a plate holder and includes a pair of edges, each of said edges being located substantially immediately below the sensitized film on one of said plates in the respective said plate holder so as to cause bubbles to be released therefrom to rise upward over the sensitized surface of said plate.

5. The apparatus of claim 2 wherein said means for applying a voltage between said plurality of first electrodes and said second electrodes is a means for applying a periodic negative voltage on said first electrodes with respect to said second electrodes.

6. The apparatus of claim 1 further comprised of a timing means, said timing means being coupled to said at least one first electrode and said second electrodes, to said means for draining, and to at least one of said means for delivering said processing fluids to said tank and adapted to automatically sequence the operation of said apparatus.

7. A processing apparatus for processing plates having a sensitized film on one surface thereof comprising:

a tank;

a rack for supporting a plurality of said plates within said tank;

at least one first electrode disposed in said tank below said rack;

a plurality of second electrodes disposed in said tank so as to each be substantially parallel to and adjacent the sensitized film on plates in said rack;

means for delivering processing fluids to said tank;

means for draining said fluids from said tank; means for applying a voltage between said at least one first electrode and said second electrodes; and

a laminar flow hood, said laminar flow hood being adapted to provide a gentle flow of filtered air over said tank to prevent the settling of airborne contamination in-said tank.

8. A photographic plate developing apparatus comprising:

a tank;

a rack for supporting a plurality of said plates within said tank;

at least one first electrode disposed in said tank below said rack and being adapted to cause bubbles to be released therefrom to rise upward over the emulsion side of said plate;

a plurality of second electrodes disposed in said tank so as to each be substantially parallel to and adjacent the emulsion coated surface on plates in said rack;

means for storing a developer solution;

means for storing a fixing solution;.

means for delivering each said developer solution and said fixing solution to said tank;

means for draining said tank;

means for applying a negative voltage on said at least one first electrode with respect to said second electrodes;

means for delivering water to said tank;

timing means coupled to said means for delivering said fixing solution, said means for draining said tank, said means for delivering water, and to said means for applying a negative voltage, to provide automatic operation thereof in a predetermined order; and

a laminar flow hood and a dryer section, said laminar flow hood being adapted to provide a gentle flow of filtered air over said tank and said dryer section, said dryer section being adapted to receive said rack and to direct warm, filtered air over plates in said rack.

9. The apparatus of claim 8 wherein said means for storing a developer solution is a second tank, said means for storing a fixing solution is a third tank and said means for delivering said developer solution and said fixing solution to said first mentioned tank are means for pressurizing said second tank and said third tanks, respectively, and for allowing fiow therefrom into said first mentioned tank.

10. The apparatus of claim 9 further comprised of a fourth tank generally surrounding said first mentioned tank, a rinsing means for directing rinse water to the outer walls of said first mentioned tank, and a rinse water delivering means for delivering water to said rinsing means, said rinse water delivering means being coupled to said timing means for automatic control thereof.

11. The apparatus of claim 10 wherein said at least one first electrode are stainless steel electrode and said second electrodes is a platinum coated titanium electrodes.

12. A photographic plate developing apparatus comprising:

a first tank;

a plurality of plate holders, each of said plate holders being adapted to support at least one plate adjacent its edges so as to allow processing solutions to freely wet both sides of said plate;

a rack for supporting a plurality of said plate holders within said tank so as to dispose said plates in said tank in a generally vertical, parallel relationship to each other;

at least one first electrode disposed in said at least one first tank below said plate holders, said first electrode having a means for encouraging the release of bubbles therefrom in lines directly under the emulsion coated surface of said plates;

a plurality of second electrodes disposed in said first tank so as to each be substantially parallel to and adjacent the emulsion coated surface of the plates in said rack;

a means for delivering water to said first tank including a first electrically operated solenoid valve for controlling said means for delivering water;

a second tank for storing a quantity of developer solution with a conduit means for delivering said developer solution to said first tank;

a third tank for storing a quantity of fixing solution with a conduit means for delivering said fixing solution to said first tank;

means for pressurizing said second tank to force developer solution into said first tank;

means for pressurizing said third tank to force fixing solution into said first tank;

a second electrically operated solenoid valve to control the flow of solution between said second tank and said first tank;

a third electrically operated solenoid valve to control the flow in said conduit between said third tank and said first tank;

a pump means for draining said first tank;

means for applying a voltage between said at least one first electrode and said second electrodes;

a fourth tank having a drain and generally surrounding said first tank;

means for spraying water on the outer surface of said first tank including a fourth electrically operated solenoid valve for controlling said means for spraying water; and

timing means coupled to said means for applying a voltage between said at least one first electrode and said second electrodes, said first, third and fourth solenoid valves and said pump means to control the operation thereof in a predetermined manner.

13. A photographic plate developing apparatus comprising:

a first tank open at the top thereof;

a plurality of plate holders, each of said plate holders being adapted to support at least one plate adjacent its edges so as to allow processing solutions to freely wet both sides of said plate;

a rack for supporting a plurality of said plate holders within said tank so as to dispose said plates in said tank in a generally vertical, parallel relationship to each other;

At least one first electrode disposed in said first tank below said plate holders, said at least one first electrode having a means for encouraging the release of bubbles therefrom in lines directly under the emulsion coated surface of said plates;

a plurality of second electrodes disposed in said first tank so as to each be substantially parallel to and adjacent the emulsion coated surface of the plates in said rack;

a means for delivering Water to said first tank including a first electrically operated solenoid valve for controlling said means for delivering water;

a second tank for storing a quantity of developer solution with a conduit means for delivering said developer solution to said first tank;

a third tank for storing a quantity of fixing solution with a conduit means for delivering said fixing solution to said first tank;

means for pressuring said second tank to force developer solution into said first tank;

means for pressurizing said third tank to force fixing solution into said first tank;

a second electrically operated solenoid valve to control the flow of solution between said second tank and said first tank;

a third electrically operated solenoid valve to control the flow of solution between said-third tank and said first tank;

a pump means for draining said first tank;

means for supplying a voltage between said at least one first electrode and said second electrodes;

a fourth tank having a drain and generally surrounding said first tank;

means for spraying water on the outer surface of said first tank including a fourth electrically operated solenoid valve for controlling said means for spraying water; and

timing means coupled to said means for applying a voltage between said at least one first and said second electrodes, said first, third electrode and fourth solenoid valves and said pump means to control the operation thereof in a predetermined manner; and' means for causing a flow of filtered air past the top of said first tank to prevent the settling of airborne contamination in said first tank.

M. The apparatus of claim 13 further comprised of a dryer section adjacent said first tank, said dryer section being adapted to receive said rack and to direct warm, filtered air over plates in said rack.

i t i i i 

2. The apparatus of claim 1 wherein said rack for supporting said plates is a rack for supporting said plates in substantially vertical and parallel planes and said at least one first electrode is a plurality of electrodes, each of which is disposed in said tank vertically below the normal position of at least one plate in said rack.
 3. The apparatus of claim 2 wherein said rack is comprised of a rack member and a plurality of removable plate holders, said rack having a means of locating said plate holders in relation thereto, said plate holders being adapted to support at least one plate adjacent its edges so as to allow processing fluids to freely wet both sides of said plate.
 4. The apparatus of claim 3 wherein said plate holders are adapted to support two plates in spaced apart parallel relationship, and each of said plurality of first electrodes is disposed below the normal position of a plate holder and includes a pair of edges, each of said edges being located substantially immediately below the sensitized film on one of said plates in the respective said plate holder so as to cause bubbles to be released therefrom to rise upward over the sensitized surface of said plate.
 5. The apparatus of claim 2 wherein said means for applying a voltage between said plurality of first electrodes and said second electrodes is a means for applying a periodic negative voltage on said first electrodes with respect to said second electrodes.
 6. The apparatus of claim 1 further comprised of a timing means, said timing means being coupled to said at least one first electrode and said second electrodes, to said means for draining, and to at least one of said means for delivering said processing fluids to said tank and adapted to automatically sequence the operation of said apparatus.
 7. A processing apparatus for processing plates having a sensitized film on one surface thereof comprising: a tank; a rack for supporting a plurality of said plates within said tank; at least one first electrode disposed in said tank below said rack; a plurality of second electrodes disposed in said tank so as to each be substantially parallel to and adjacent the sensitized film on plates in said rack; means for delivering processing fluids to said tank; means for draining said fluids from said tank; means for applying a voltage between said at least one first electrode and said second electrodes; and a laminar flow hood, said laminar flow hood being adapted to provide a gentle flow of filtered air over said tank to prevent the settling of airborne contamination in said tank.
 8. A photographic plate developing apparatus comprising: a tank; a rack for supporting a plurality of said plates within said tank; at least one first electrode disposed in said tank below said rack and being adapted to cause bubbles to be released therefrom to rise upward Over the emulsion side of said plate; a plurality of second electrodes disposed in said tank so as to each be substantially parallel to and adjacent the emulsion coated surface on plates in said rack; means for storing a developer solution; means for storing a fixing solution; means for delivering each said developer solution and said fixing solution to said tank; means for draining said tank; means for applying a negative voltage on said at least one first electrode with respect to said second electrodes; means for delivering water to said tank; timing means coupled to said means for delivering said fixing solution, said means for draining said tank, said means for delivering water, and to said means for applying a negative voltage, to provide automatic operation thereof in a predetermined order; and a laminar flow hood and a dryer section, said laminar flow hood being adapted to provide a gentle flow of filtered air over said tank and said dryer section, said dryer section being adapted to receive said rack and to direct warm, filtered air over plates in said rack.
 9. The apparatus of claim 8 wherein said means for storing a developer solution is a second tank, said means for storing a fixing solution is a third tank and said means for delivering said developer solution and said fixing solution to said first mentioned tank are means for pressurizing said second tank and said third tanks, respectively, and for allowing flow therefrom into said first mentioned tank.
 10. The apparatus of claim 9 further comprised of a fourth tank generally surrounding said first mentioned tank, a rinsing means for directing rinse water to the outer walls of said first mentioned tank, and a rinse water delivering means for delivering water to said rinsing means, said rinse water delivering means being coupled to said timing means for automatic control thereof.
 11. The apparatus of claim 10 wherein said at least one first electrode are stainless steel electrode and said second electrodes is a platinum coated titanium electrodes.
 12. A photographic plate developing apparatus comprising: a first tank; a plurality of plate holders, each of said plate holders being adapted to support at least one plate adjacent its edges so as to allow processing solutions to freely wet both sides of said plate; a rack for supporting a plurality of said plate holders within said tank so as to dispose said plates in said tank in a generally vertical, parallel relationship to each other; at least one first electrode disposed in said at least one first tank below said plate holders, said first electrode having a means for encouraging the release of bubbles therefrom in lines directly under the emulsion coated surface of said plates; a plurality of second electrodes disposed in said first tank so as to each be substantially parallel to and adjacent the emulsion coated surface of the plates in said rack; a means for delivering water to said first tank including a first electrically operated solenoid valve for controlling said means for delivering water; a second tank for storing a quantity of developer solution with a conduit means for delivering said developer solution to said first tank; a third tank for storing a quantity of fixing solution with a conduit means for delivering said fixing solution to said first tank; means for pressurizing said second tank to force developer solution into said first tank; means for pressurizing said third tank to force fixing solution into said first tank; a second electrically operated solenoid valve to control the flow of solution between said second tank and said first tank; a third electrically operated solenoid valve to control the flow in said conduit between said third tank and said first tank; a pump means for draining said first tank; means for applying a voltage between said at least one first electrode and said second electrodes; a fourth tank having a drain and generally surrounding said first tank; means for spraying water on the outer surface of said first tank including a fourth electrically operated solenoid valve for controlling said means for spraying water; and timing means coupled to said means for applying a voltage between said at least one first electrode and said second electrodes, said first, third and fourth solenoid valves and said pump means to control the operation thereof in a predetermined manner.
 13. A photographic plate developing apparatus comprising: a first tank open at the top thereof; a plurality of plate holders, each of said plate holders being adapted to support at least one plate adjacent its edges so as to allow processing solutions to freely wet both sides of said plate; a rack for supporting a plurality of said plate holders within said tank so as to dispose said plates in said tank in a generally vertical, parallel relationship to each other; At least one first electrode disposed in said first tank below said plate holders, said at least one first electrode having a means for encouraging the release of bubbles therefrom in lines directly under the emulsion coated surface of said plates; a plurality of second electrodes disposed in said first tank so as to each be substantially parallel to and adjacent the emulsion coated surface of the plates in said rack; a means for delivering water to said first tank including a first electrically operated solenoid valve for controlling said means for delivering water; a second tank for storing a quantity of developer solution with a conduit means for delivering said developer solution to said first tank; a third tank for storing a quantity of fixing solution with a conduit means for delivering said fixing solution to said first tank; means for pressuring said second tank to force developer solution into said first tank; means for pressurizing said third tank to force fixing solution into said first tank; a second electrically operated solenoid valve to control the flow of solution between said second tank and said first tank; a third electrically operated solenoid valve to control the flow of solution between said third tank and said first tank; a pump means for draining said first tank; means for supplying a voltage between said at least one first electrode and said second electrodes; a fourth tank having a drain and generally surrounding said first tank; means for spraying water on the outer surface of said first tank including a fourth electrically operated solenoid valve for controlling said means for spraying water; and timing means coupled to said means for applying a voltage between said at least one first and said second electrodes, said first, third electrode and fourth solenoid valves and said pump means to control the operation thereof in a predetermined manner; and means for causing a flow of filtered air past the top of said first tank to prevent the settling of airborne contamination in said first tank.
 14. The apparatus of claim 13 further comprised of a dryer section adjacent said first tank, said dryer section being adapted to receive said rack and to direct warm, filtered air over plates in said rack. 